You will get a lot of varying opinions here in part because everybody's eyes are different and also because different power settings affect outcome. But generally speaking, if you compare equal quality glass with them both on the same power you will gain a few more minutes at dusk and dawn. In my experience it is less than 10 minutes and more like 5 or 6 minutes.
The advantage of the 50 comes in if you need high power in the last few minutes of light. Otherwise, there isn't a lot of benefit. There are drawbacks however, like a higher mount (harder for good cheek weld), and heavier scope.